Electric brake for elevators



(No Model.)

J.P.GA SEY. ELECTRIC BRAKE FOR ELEVATORS.

Patented Nov. 16, 1897.

but this would require a very large coil to FFICE.

PATENT JOHN P. CASEY, OF BLOOMSBURG, PENNSYLVANIA.

ELECTRIC BRAKE FOR ELEVATORS.

SPECIFICATION forming part of Letters Patent No. 593,832, dated November 16, 1897.

Application filed August 23,1894.

T0 at whom it may concern:

Be it known that I, JOHN P. CASEY, of the city of Bloomsburg, county of Columbia, and State of Pennsylvania, have invented an Improvement in Electric Brakes for Elevators, &c., of which the following is a specification. 7 My invention has reference to electric brakes for elevators, 850.; and it consists of certain improvements which are fully set forth in the following specification and shown in the accompanying drawings, which form a part thereof.

The invention forming the subject-matter of this application more particularly comprehends certain improvements in the brakecontrolling devices adapted to apply the brake to the power-shaft when the motor is thrown out of operation and vice versa.

The object of my improvements is to provide an electricallyoperated brake which shall positively apply or remove the braking friction and which shall be independent of any variation in the flow of current through the motor due to its variable speed. Heretofore considerable difiiculty has arisen in applying the electric brake to an electricallyactuated elevator from the fact that when the brake-solenoid is in series with the motor or armature thereof the variations in the speed of the armaturesuch, for instance, as take place when the elevator is descending-produce a higher counter electromotive force, which checks the current flowing through the brake-solenoid to such an extent as to unintentionally apply the brake, the said brake being applied at a time when it is desirable to keep it out of action. This difficulty is always liable to happen where a single coil is employed tooperate the brake and when the brake is in series with the motor-armature. The difficulty can be obviated by employing the shunt-coil as the solenoid for the brake,

work with any economy and to make the brake quickly responsive. These defects are entirely overcome by the use of my invention, because by employing a compound winding for my brake-magnet I may have the low resistance-coil in series with the armature 0f. the motor and the high-resistance shunt-coil Serial No. 621,088. (No model.)

in parallel with the armature. The action of this construction is that the large current flowing through the armature causes instantaneous action on the brake-core to remove the brake, and the energy of the high-resistance shunt-coil causes the core to remain in position to keep the brake out of action when once it has been drawn into the solenoid and until the motor-circuit is broken. It will be understood that the high-resistance coil has practically nothing to do except hold the core in its raised position after the work has been accomplished by the series solenoid, whereby the current in the series solenoid or armature of the motor may vary within wide limits without permitting the brake to be accidentally applied.

My improvements are adapted, in connection with any braking device, for any class of machinery, though I have shown it especially adapted to electric elevators as illustrating an advantageous use of the said improvement.

The general construction of the apparatus will be better understood by reference to the accompanying drawings, in which- Figure 1 is a side elevation of an electric elevator embodying my improvements. Fig. 2 is a front elevation of my improved braking device with the power-shaft in section, and Fig. 3 is a transverse section through the friction-brake pulley and band.

A is the winding-drum adapted to take up and pay out the cable l3, which leads to the cage or any movable device. The said drum A is rotated by means of worm and wormwheel gearing C, the latter being operated through the power-shaft c and the electric motor D. A switch-lever N and contacts 1, 2, 3, 4, 5, and 6 control the current from the main conductors O, branch conductors P R, armature-circuit T, and field-magnet circuit S, whereby the motor may be caused to be put into and out of operation and reversed as to its direction of rotation. The positive conductor of the line-circuits O is connected by branch circuit P with the two contacts 3 3. The negative-line conductor is connected by the branch circuits R R with the two contacts 5 5. The terminals of the fieldmagnets of the motor are respectively connected with the contacts 4; 4: G 6. The terminals of the armature-circuits T are connected to the contacts 1 and 2 of the switch I. IVhen the switch is thrown in connection with one set of terminals 3 4 5 G, the motor D rotates in one direction. lVhen the said switch is thrown in connection with the other set of terminals 3 at 5 6, the motor runs in the reverse direction. In one of these cases the drum A winds up the cable and in the other case it pays out said cable.

It is to be understood that the controllingswitch may be made in any suitable manner, the illustration herein given being simply an example without reference to the details.

E is a brake-pulley secured to the power shaft 0. F is a brake-band encircling said pulley and connected at the bottom to the standard 6. The upper ends of the band are slightly separated and are connected to the short arms of toggle-levers G G, the long arms of which are connected with the verticallymoving magn etie core II. The core II works in a solenoid arranged within an iron easing I, bolted to the frame of the machine. The top of said casing I should be of iron to increase the magnetic field necessary to raise the core II. The core II is made sufficiently heavy, so that when it is allowed to fall it will apply the brake-band F to the brake-pulley. This core therefore performs not only the function of operating the toggles to remove the brake, but also constitutes the weight adapted to apply the brake. The solenoid is compound wound and consists of a high-resistance coil J and a low-resistance coil K. The low-resistance coil K is in series with the armature and armature-circuit T, so that the current traversing the armature also traverses the low-resistance coil K of the brake-magnet. The high-resistance coil J is in shunt relation to the armature and low-resistance coil and is supplied with current by shunteircuit IV. The construction is such that when the switch N is thrown to open the motor-circuit it also opens the brake-magnet circuits and completely cuts all of the parts out of the line-circuit.

M is a dash-pot having a plunger Z working therein and connected by a rod L with the head of the core II, as more clearly shown in Fig. 2. This dash-pot I\[ is adapted to cause the core II to move deliberately for the purpose of applying the brake-band gradu ally and thereby prevent any injury to the apparatus due to sudden stoppage.

In operation, when the switch N is thrown to close the circuit through the motor, as indicated, the current traverses the low-resistance coil K and armature simultaneously with the current passing through the high-resistance coil J in shuntcircuit. The combined action of the solenoid-coils instantly vator. brought near the iron cap of the ease I, and will require but little power to hold itin said raised position. This power is readily supplied by the shunt-coil, which holds the said core in its elevated position and the brake out of action so long as the motor is in circuit, and this action takes place irrespective of the amount of current flowing through the armature. The motor may run at variable speeds under this construction, generating proportionally variable counter electromoti ve force and changing to any extent the current flowing through the series or low-resistance coils of the brake-magnet without danger of applying the friction-brake to the power shaft.

It is evident that the mechanical or friction brake may be of any suitable construction, as numerous mechanical devices for this purpose are well known, and any of them may be adapted to my improvements. The construction illustrated I have found to be excellently adapted to the purpose, however.

"While I have shown a shunt-wound motor for operating elevator or hoisting devices, it is to be understood that a series or compound wound motor may be employed in lieu thereof.

While I prefer the construction shown, I do not limit myself to the minor details thereof, as they may be modified in various ways without departing from the principles of my invention.

Having now described my invention, what I claim as new, and desire to secure by Let ters Patent, :is

1. The combination of a power-shaft, an electric motor to rotate said shaft, a friction gravity-brake adapted to arrest the rotation of said shaft, an electromagnetic device for removing the said brake provided with high and low resistance coils for producing the same polarities in the electromagneticdevices, an electric circuit includin g the low-resistance coil in series with the armature, a shunt-circuit including the high-resistance coil in shunt relation with the armature of the motor, and a switch device for controlling the flow of current through said circuits for always maintaining the current flowing in both coils of the brake-magnet in the same direction at any moment of time.

2. The combination of a power-shaft, a me chanical brake therefor, a vertically-movable magnetic core to apply the brake by the weigh t of said core, a casing for said core, a compound winding arranged on said casing and. composing high and low resistance coils adapted to produce similar polarities at all times, current translating or consuming devices in series with the low-resistance coil, and switch devices for controlling the current to said coils so that it flows through them always in the same direction at any moment of time, whereby the current flowing through the low-resistance coil may raise the core of Nhen the core II is raised, it will be the brake to remove the brake, and the eur- In testimony of which invention I have rent flowing through the high-resistance coil hereunto set my hand. may assist in maintaining the brake in its elevated position irrespective of variations in JOHN CASEY 5 the current flowing through the low-resist- Witnesses:

ance coil due to any action of the translating JOHN L. WOODS,

or current-consuming devices. 8., 0. BROWN. 

